On Fri, Jun 27, 2025 at 8:39 PM Adrian Godwin via cctalk <cctalk@classiccmp.org> wrote: > > Interesting that some readers didn't require the sprocket hole. Whilst
I have never seen a paper tape reader that didn't use the sprocket hole as some kind of reference. Either by driving the tape using it or by detecting it along with the data holes. > I can appreciate that they didn't mechanically drive on it, I assumed > they'd use it as a clock signal to sample the data levels. Even that > could be avoided, but then a nul would be indistinguishable from the > space between punch positions. > > Did they make nul an illegal character, or determine it using a > flywheel sync ? I appreciate there were out-of-band ASCII characters > such as EOT but weren't there binary format tapes too ? Card readers (a totally blank column is legal on a normal 80 column card) took a reference from the leading edge of the card and re-synced whenever holes were found (see the Documation manuals on bitsavers, for example). But paper tape? You could re-sync on the data holes and hope for the best but why on earth would anyone bother when every paper tape has the sprocket holes? If a paper tape reader that doesn't need sprocket holes exists, could somebody post the make/model and preferably a link to a manual for it. -tony
